Water is a increasingly popular drink, and is used to brew other drinks such as coffee, tea and espresso. Water vapor or steam is used to heat and froth milk for making cappuccino, latte and other drinks containing milk. Water filtration is known to improve water taste and the taste of drinks made from the filtered water. Water filtration pitchers has been increasingly used to filter water for either direct consumption or for use with automatic drip coffeemakers in preparing coffee. Water filtration have also been integrated into automatic drip coffeemakers by forming a cavity at the outlet of the water reservoir for receiving a water filter cartridge and directing the filtered water to the water heater as soon as it exits the cartridge. Such arrangement has several drawbacks. First, it can not provide a supply of filtered water as quickly as required by apparatus like espresso/cappuccino machines and those disclosed in U.S. Pat. No. 5,267,506. Second, it has low filtration efficiency because it can only use relatively large activated carbon particles to achieve the flow rate required by the automatic drip coffeemakers. Third, none of the current coffeemakers can produce filtered water for direct consumption. Forth, a partially clogged water filter cartridge will change the water flow rate through the water heaters of the automatic drip coffeemakers, thus may cause changes in coffee temperature and taste. Fifth, the water filter cartridge provide a bed for bacteria growth and may produce foul odor. At last, the water filter cartridge can not remove the plastic odor and impurities in the water which result from contacting the plastic, rubber and metal parts of the apparatus. U.S. Pat. No. 5,393,548 discloses a device and method for filtering impurities from the water by positioning a water filtration device between the hot water drip outlet of an automatic drip coffeemaker and the ground coffee in a filter. This device and method resolved to some degree the fourth and sixth drawbacks mentioned above with the existing water filter systems for automatic drip coffeemakers, but it caused additional problems including that water may overflow the top of the device and get to the ground coffee unfiltered and that the device may be covered with ground coffee and cause additional cleaning work for the consumers.
Currently, none of the commercially available espresso and cappuccino machines have water filter system, although the consumers who drink espresso-based beverages like espresso, latte and cappuccino are normally more conscious to coffee quality and taste than the consumers who drink only regular coffee. There is currently no known water filtration system which can be adapted to the espresso and cappuccino machines and the apparatus disclosed in U.S. Pat. No. 5,267,506 without major inventive modifications. There is neither known water filtration system for producing purified water for producing steam for frothing milks for making milk-containing drinks like cappuccino and latte.
Cappuccino, latte and other milk-containing drinks are made by adding espresso into milk, or vice versa. Prior to mixing milk with espresso, the milk is frothed with a jet of steam to produce a foamy head and to heat the milk to a desired temperature. The simplest frothing device consists of a steam tube having an orifice at one end for producing a steam jet. The espresso machine operators position the orifice just below the surface of milk and bobs the milk container up and down to inject air into the milk. After enough foam is produced, the steam tube is inserted down into the milk to further heat the milk without producing more foam. Here, experience is crucial to obtain satisfactory results because if you have the nozzle too deeply into the milk there will be no foam, if you have it too shallow it will spray milk all over.
A first modified form of the frothing device, as disclosed in U.S. Pat. Nos. 4,735,133, 4,800,805, 4,945,824, and 5,335,588, has an air tube with a first end next to the orifice of the steam tube and a second end far above the surface of milk, thus making air available to the milk near the steam orifice even if the orifice is immersed in the milk. The air tube is very restrictive to reduce and control the flow of air into the tube. One problem arises with this modified frothing device in that after the milk container is full of foam or after the desired amount of foam has been produced, it is difficult to further heat the milk without producing more foam. Consequently, you may have to either satisfy with a lukewarm milk or suffer a mess caused by milk overflowing. A second problem with this device is that the air tube is very vulnerable to clogging by milk, dusts, etc., thus making the frothing operation inconsistent and frustrating. A third problem arises with this device in that there are various types of milk and they may require more or less air flow to achieve optimum frothing. To correct the third problem, the air tube needs a valve to adjust the air flow, which makes the device complex and difficult to use.
A second modified form of the frothing device, as disclosed in U.S. Pat. Nos. 4,779,519, 4,949,631, 5,265,519 and 5,330,266, comprises a chamber having a steam inlet, an air inlet, a milk inlet and an outlet for the above three fluids. The steam gushing from the steam inlet aspirates and entrains, by the venturi effect, the air from the air inlet and the milk from the milk inlet. The air from the air inlet, steam from the steam inlet and milk from the milk inlet are mixed in the chamber or in an extension of the chamber to produce an emulsion or frothed milk, which flows out of the outlet of the chamber and is collected in a container for use in making cappuccino, latte, and other heated drinks. To avoid the lack of foam in the frothed milk due to too little air or big air bubbles due to too much air into the chamber via the air inlet, Marano-Ducarne (U.S. Pat. No. 5,738,002) and Stubaus (U.S. Pat. No. 5,330,266) taught various means to control the air flow into the chamber. To avoid inconsistent temperature of the frothed milk due to variation in milk flow rate into the chamber from a cold milk supply, Grossi (U.S. Pat. No. 5,862,740) taught a valve to control the cold milk flow rate into the chamber. There are several critical problems with such modified milk frothing devices. First, the air inlet in such modified milk frothing devices must be small and is thus subject to clogging by milk and particles, which greatly reduces the reliability and increase the chance of product returns by the consumers. Second, to meet the consumer needs to froth the different types of milks such skim, low fat and regular milks, to obtain different amount of foam, or to achieve different milk temperatures, these modified devices need valves to adjust the air and milk flow into the chamber, which complicates the device and the operation. Thirdly, such modified frothing device is sensitive to operation variables such as steam flow rate, the liquid level and temperature of the cold milk supply, vacuum level in the chamber and partial clogging of the air or milk inlet. As a result, the frothed milk often has inconsistent quality in terms of temperature, foam quantity and other important characteristics. At last, these modified devices are normally very noise due to the mixing of air, milk and steam in the chamber and release significant amount of steam during the frothing operation, which sometimes intimidates and confuses the operators.
A third modified form of the frothing device involves a spinning blade at the end of the steam tube. Steam whirls the blade like a miniature turbine to break air bubbles into smaller ones to stabilize the resulting foam. This method, however, requires the operators to keep moving the milk container downward during frothing process to ensure that the air vent in the blade attachment is just at the surface of the milk.
The present invention provides apparatus having novel and improved means for making filtered water either for direct consumption or for use in preparing drinks such as espresso, coffee, cappuccino and latte and for automatically frothing milk, and is aimed at solving the problems associated with the existing apparatus for making such drinks.